A case of superficial acral fibromyxoma masquerading as squamous cell carcinoma of the thumb: A case report

A wide spectrum of tumors may affect the periungual spaces of the digits. Superficial acral fibromyxoma (SAF) is a rare, benign soft tissue tumor with diverse clinical presentations. We present a case of a 55-year-old woman with a 2-year history of a solitary periungual tumor on the left thumb, subjected to multiple episodes of trauma. Initially suspected to be a periungual squamous cell carcinoma (SCC) based on clinical and dermoscopic features, the tumor was confirmed to be a CD34⁻ SAF through histopathology and immunohistochemistry. Although CD34 immunoreactivity is common in SAF, one-third of these tumors, including this case, do not stain for this marker. Periungual SCC considered a “great mimicker of nail tumors,” may resemble other benign nail tumors such as SAF. The patient underwent complete surgical excision with primary closure, resulting in no recurrence after 1 year. This case highlights SAF as an underrecognized benign entity that may manifest with features suspicious of malignancy, potentially leading to unnecessarily aggressive interventions. Recognizing SAF through accurate biopsy techniques and thorough histopathologic evaluation, even in the absence of CD34 reactivity, is crucial for appropriate treatment and preservation of hand function and appearance.